A sign hangs at a branch of Burger King in central London. / Kirsty Wigglesworth, AP

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

LONDON â?? Burger King has found traces of horse DNA at a plant that supplied its U.K. beef patties, the restaurant chain has said.

In a Thursday statement, Burger King said "four samples recently taken from the Silvercrest plant (in Ireland) have shown the presence of very small trace levels of equine DNA."

The statement added, "Within the last 36 hours, we have established that Silvercrest used a small percentage of beef imported from a non-approved supplier in Poland. They promised to deliver 100% British & Irish beef patties and have not done so. This is a clear violation of our specifications, and we have terminated our relationship with them. "

Burger King said that the meat did not did make its way to the firm's restaurants.

"While the Food Safety Authority of Ireland has stated that this is not a food safety issue, we are deeply troubled by the findings," said Diego Beamonte, Burger King's vice president of global quality.

As a precaution, the fast food company said it is now using suppliers in Germany and Italy.

Last month, Burger King said that its patties were made from 100% beef following the revelation that the British supermarket chain Tesco had sold burgers that were discovered to contain traces of horse meat.